Modulus of Elasticity and Poisson Ratio of Concrete

Modulus of Elasticity and Poisson Ratio of Concrete Benjie Cho and Mulugojam Alemu Undergraduate Civil Engineering Univ. . of Southern California

Objective Find the Modulus of Elasticity of Concrete l Find Poisson’s Ratio of Concrete l

Introduction l Compressive Strength of Concrete – Standardardized test of concrete l American Society for Testing and Materials (ASTM) – Specifications include l Correct mix l Properly affixing strain gauges l Properly capping the cylinder with sulfur

Procedure Select (5) 4 in diameter by 12 in length concrete with 28 -day age with 4 ksi design strength. l Cap all the bearing surfaces with sulfur to make the end flat. l Mark area where strain gauges will be attached. l Clean area with chemical cleaners and sand paper. l

Procedure l l l Affix strain gauges on their designated area, one vertical and one horizontal, using glue. Attach wire to strain gauges by soldering. Test voltage of the strain gauges. Place and center samples on the Satec Universal Testing Machine. Connect the wires to the P 3500 strain indicator, which in turn is connected to a computer for recording.

Procedure Set gauge factor to 2. 055 +/-. 5% and zero the strain readings. l Begin loading the specimens and record values of strain for given loads. l Continue testing until failure of the specimen. l

Organizing the data Compute the stress by dividing the load by the cross-sectional area. l Graph the strength against the vertical and horizontal strains of each specimen. l Find values for the Young’s Modulus and Poisson’s ratio from the data. l Calculate theoretical values the Young’s Modulus and Poisson’s ratio. l

Calculation procedures l Young’s Modulus – E=(s 1 -s 2)/(e 2 -. 000005) l s 1=The stress corresponding to the longitudinal strain of 50 micro strain. l s 2=The stress corresponding to. 4 f ‘c. l E 2=The longitudinal strain corresponding to s 2. l Based on ASTM C 469 l Poisson’s Ratio – n=(Lateral Strain)/(Longitudinal Strain)

Example

Cylinder #2

Cylinder #3

Cylinder #4

Cylinder #5

Selected Values of Stress and Strain

Selected Values of Stress and Strain

Data

Conclusion All specimens performed under theorectical values of E. – Average E= 2. 60 E 6 psi l Average Poisson Ratio=. 119691 l

Conclusion l Concrete performed to design specifications. – E= 1. 5 - 5 ksi – n=. 1 l Xiao, Yan. Experimental Analysis of Engineering Materials. University of Southern California lecture notes 2002.